1. Center for Condensed Matter Sciences and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan
2. Department of Engineering, University of Massachusetts Boston, Boston, Massachusetts 02125, USA
3. Sensors Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, USA
4. Department of Electronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 807, Taiwan
5. Institute of Applied Research, Vilnius University, Saulėtekio al. 9-III, LT-10222 Vilnius, Lithuania
6. Riga Technical University, 3/7, Paula Valdena Str., LV-1048 Riga, Latvia